Kashiwakura Ikuo, Inanami Osamu, Takahashi Kenji, Takahashi Tsuneo A, Kuwabara Mikinori, Takagi Yoshinari
Department of Radiological Technology, Hirosaki University School of Health Sciences, 66-1 Hon-cho, Hirosaki, Aomori 036-8564, Japan.
Radiat Res. 2003 Aug;160(2):210-6. doi: 10.1667/3032.
In previous studies we characterized the radiosensitivity of CFU-megakaryocytes from human placental and umbilical cord blood and the effects of various early-acting cytokines. We found that the maximal clonal growth of CFU-megakaryocytes in vitro and maximal protection against X-ray damage were supported by a combination of thrombopoietin and stem cell factor. However, the mechanism by which the two cytokines exert a synergistic effect remained unclear, so we extended these studies to investigate the radioprotective action of synergistic thrombopoietin and stem cell factor on the survival of X-irradiated CD34(+) CFU-megakaryocytes. A combination of thrombopoietin and stem cell factor led to activation of mitogen-activated protein kinase and extracellular signal-regulated protein kinase and to suppression of caspase 3 in X-irradiated CD34(+) cells. When PD98059 and various synthetic substrates-specific inhibitors of these proteins-were used, the combination had less effect on the clonal growth of X-irradiated CD34(+) CFU-megakaryocytes. However, the addition of wortmannin, a specific inhibitor of the phosphatidylinositol-3 kinase pathway, did not alter the synergistic action of thrombopoietin plus stem cell factor. We suggest that part of this synergistic effect can be explained by activation of mitogen-activated protein kinase and extracellular signal-regulated protein kinase and by suppression of the caspase cascade.
在先前的研究中，我们对来自人胎盘和脐带血的巨核细胞集落形成单位（CFU-巨核细胞）的放射敏感性以及各种早期作用细胞因子的影响进行了表征。我们发现，血小板生成素和干细胞因子的组合可支持CFU-巨核细胞在体外的最大克隆生长以及对X射线损伤的最大保护作用。然而，这两种细胞因子发挥协同作用的机制仍不清楚，因此我们扩展了这些研究，以研究血小板生成素和干细胞因子协同作用对经X射线照射的CD34(+) CFU-巨核细胞存活的辐射防护作用。血小板生成素和干细胞因子的组合导致经X射线照射的CD34(+)细胞中丝裂原活化蛋白激酶和细胞外信号调节蛋白激酶的激活以及半胱天冬酶3的抑制。当使用PD98059和这些蛋白的各种合成底物特异性抑制剂时，该组合对经X射线照射的CD34(+) CFU-巨核细胞的克隆生长影响较小。然而，加入磷脂酰肌醇-3激酶途径的特异性抑制剂渥曼青霉素并没有改变血小板生成素加干细胞因子的协同作用。我们认为，这种协同作用的部分原因可以通过丝裂原活化蛋白激酶和细胞外信号调节蛋白激酶的激活以及半胱天冬酶级联反应的抑制来解释。
